The long-term objective of this research is to define the molecular mechanisms of sperm and egg interactions operative in fertilization. The specific aims during this grant period are: 1) Identify and define the molecular mechanism responsible for egg envelope transformations that underlie the ultrastructural and sperm penetrability changes in egg envelopes isolated from the frog, Xenopus laevis. The oviducal and egg cortical granule constituents responsible for these changes, presumably enzymes, will be isolated. In vitro envelope transformations will be effected using the isolated enzymes. 2) The glycoprotein envelope components that function as ligands for sperm receptors will be identified. Methodologically, binding of isolated 125I-envelope components and chemical cross-linking of sperm receptor-envelope ligand using bifunctional protein reagents will be used to ascertain the binding partners. Gametes from Xenopus laevis and from the domestic pig, Sous crofa, will be used. 3) We will continue the chemical characterization of the glycoproteins composing the pig zona pellucida and identify which components are antigenic. The zona pellucida components will be isolated and their antigenicity determined using monoclonal antibody techniques. Correlation of the structural and functional properties of the zona pellucida glycoproteins will provide information that can be used to control sperm-egg interactions.